Improving Li⁺ Transport in PTFE-Based Dry Thick Electrodes through PEG Co-Binder Engineering

Dry process based thick electrodes are considered a promising strategy for improving the volumetric energy density of lithium-ion batteries. However, increasing electrode thickness often causes limited electrolyte penetration, increased interfacial resistance, and sluggish Li⁺ ion transport, resulting in deteriorated electrochemical performance. In this study, polyethylene glycol (PEG) was introduced as a co-binder into a PTFE-based dry thick electrode system to improve electrode-electrolyte interfacial properties without altering the electrode structure. Contact angle analysis confirmed that PEG incorporation enhanced electrolyte wettability, while XRD, BET, and pristine SEM analyses showed no significant changes in the crystal or pore structure of the electrodes. Electrochemical analyses revealed that PEG incorporation reduced interfacial resistance and improved Li⁺ transport kinetics. EIS results showed decreased Rs and Rct values with increasing PEG content, and GITT analysis demonstrated reduced IR drop and faster voltage relaxation behavior. In addition, PEG-containing electrodes exhibited reduced polarization and improved rate capability compared to the pristine electrode. Among the samples, the LFP-PEG20 electrode showed the lowest interfacial resistance and the best high-rate performance. Furthermore, ex-situ SEM analysis revealed a more uniform reaction environment in the PEG-containing electrodes, consistent with the improved electrolyte affinity and Li⁺ transport behavior. These results demonstrate that the PEG-based co-binder strategy effectively improves interfacial interactions and electrochemical performance in dry thick electrodes without inducing structural changes, providing a promising approach for high-energy-density lithium-ion batteries